The present invention disclosed herein relates to security and surveillance, and more particularly, to a security surveillance system and method capable of separately detecting fire and intrusion situations on the basis of a sound field variation.
A security sensor used for sensing fire or intrusion situation has been researched for a long time.
A sensor sensing fire may use one of a temperature sensing scheme, a smoke sensing scheme, a gas sensing scheme, and a flame sensing scheme. On the other hand, a sensor for sensing intrusion may use one of a passive infrared (PIR) sensing scheme, an IR sensing scheme, an ultrasonic scheme, a sound sensing scheme, a vibration sensing scheme, and a microwave sensing scheme.
Recently, an image surveillance system using camera imaging information, such as a CCTV, an internet protocol (IP) camera, or a vehicle blackbox is largely used in a security surveillance field.
Typically, an intrusion detector detecting a sound pressure variation to detect intrusion is known. When counting the number of times that a difference between detected sound pressure and reference sound pressure exceeds a predetermined value and determining that the counted number of times is a preset reference number or greater, the intrusion detector generates an output for determining the intrusion. The intrusion detector may detect even intrusion without sound. However, the intrusion detector is required to determine intrusion criterions variably according to spatial or environmental conditions. Furthermore, the intrusion detector does not discriminate intrusion from fire.
In another case, there is a combined fire detector detecting smoke, a flame, and fire. The combined fire detector detects the smoke, flame, and the fire by means of one integrated fire detector. The combined fire detector has a smoke sensing function for preparing for spontaneous combustion together with a flame detecting function for preparing arson.
This combined fire detector may have a low false reporting ratio with respect to various fire situations and detect fire in an early state when it is installed at a location where a flame or smoke is directly detected. However, this combined fire detector does not detect fire well in an early fire state when a temperature or smoke density at a sensor installed location is not high. In addition, when a flame is covered with an object or fire breaks out at a blind spot, the combined fire detector is difficult to detect fire in an early state because of difficulty of detecting a flame.
In another case, a fire surveillance method and system based on a sound field variation may detect a sound field variation inside a fire surveillance space to detect fire in an early state. Here, the sound field variation is caused by a fact that changes in air density and sound wave speed according to a temperature change of surrounding air due to the fire affect sound wave transfer. Although this sound field variation based fire detecting scheme may detect outbreak of fire on the basis of the sound field variation due to the fire, it is difficult to detect a temperature distribution change in detail and quantitatively. Accordingly, it is difficult to exactly discriminate fire from intrusion, wherein they are main causes of the sound field variation.
In another case, there is a security scheme through a sound field pattern analysis. This security scheme detects a sound field variation and detects intrusion based on a sound pressure variation rate with respect to a standard deviation by detecting a deviation and an average of sound pressure. Furthermore, reliability for security surveillance is increased by detecting a pattern of the sound field variation according to a time change or a wavelength change of a sound source.
However, even in this method, due to difficulty of detecting a temperature distribution change in detail and quantitatively, it is still difficult to discriminate fire from intrusion, wherein they are main causes of the sound field variation.